Focusing of geodetic instruments has for some time been effected by means of a focusing lens mounted in a draw tube located within the telescope near the objective end. Axial displacement of the draw tube by means of a rack and pinion mechanism driven from an external knob has been typical of these previously available telescope focusing means. Representative of such focusing mechanisms is that shown in U.S. Pat. No. 3,220,297. The rather awkward focusing operation which required the operator to move his attention from the sighted target in order to acquire the focusing knob has been obviated in the focusing mechanism of the present invention.